4A Low Quiescent Current 1MHz High Efficiency Synchronous Buck Regulator

Transcription

1 4A Low Quiescent Current 1MHz High Efficiency Synchronous Buck Regulator NOT RECOMMENDED FOR NEW DESIGNS RECOMMENDED REPLACEMENT PART ISL8014A ISL8014 The ISL8014 is a high efficiency, monolithic, synchronous stepdown DC/DC converter that can deliver up to 4A continuous output current from a 2.7V to 5.5V input supply. It uses a current control architecture to deliver very low duty cycle operation at high frequency with fast transient response and excellent loop stability. The ISL8014 integrates a pair of low ONresistance PChannel and NChannel internal MOSFETs to maximize efficiency and minimize external component count. The 100% dutycycle operation allows less than 400mV dropout voltage at 4A output current. High 1MHz pulsewidth modulation (PWM) switching frequency allows the use of small external components and SYNC input enables multiple ICs to synchronize out of phase to reduce ripple and eliminate beat frequencies. The ISL8014 can be configured for discontinuous or forced continuous operation at light load. Forced continuous operation reduces noise and RF interference while discontinuous mode provides high efficiency by reducing switching losses at light loads. Fault protection is provided by internal hiccup mode current limiting during short circuit and overcurrent conditions, an output over voltage comparator and overtemperature monitor circuit. A power good output voltage monitor indicates when the output is in regulation. The ISL8014 is offered in a space saving 4x4 QFN lead free package with exposed pad lead frames for low thermal. The ISL8014 offers a 1ms PowerGood (PG) timer at powerup. When shutdown, ISL8014 discharges the output capacitor. Other features include internal softstart, internal compensation, overcurrent protection, and thermal shutdown. The ISL8014 is offered in a 16 Ld 4mmx4mm QFN package with 1mm maximum height. The complete converter occupies less than 0.4in 2 area. Features High Efficiency Synchronous Buck Regulator with up to 97% Efficiency PowerGood (PG) Output with a 1ms Delay 2.7V to 5.5V Supply Voltage 3% Output Accuracy OverTemperature/Load/Line 4A Output Current Pin Compatible to ISL8013 Startup with PreBiased Output Internal SoftStart 1ms SoftStop Output Discharge During Disabled 35µA Quiescent Supply Current in PFM Mode Selectable Forced PWM Mode and PFM Mode External Synchronization up to 4MHz Less than 1µA Logic Controlled Shutdown Current 100% Maximum Duty Cycle Internal Current Mode Compensation Peak Current Limiting and Hiccup Mode Short Circuit Protection OverTemperature Protection Small 16 Ld 4mmx4mm QFN PbFree (RoHS Compliant) Applications DC/DC POL Modules µc/µp, FPGA and DSP Power Plugin DC/DC Modules for Routers and Switchers Portable Instruments Test and Measurement Systems Liion Battery Powered Devices Small Form Factor (SFP) Modules Bar Code Readers ISL8014 FN CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1888INTERSIL or Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc All Rights Reserved All other trademarks mentioned are the property of their respective owners.

2 Ordering Information PART NUMBER (Notes 1, 2, 3) PART MARKING TEMP. RANGE ( C) PACKAGE (PbFree) PKG. DWG. # ISL8014IRZ 80 14IRZ 40 to Ld 4x4 QFN L16.4x4 NOTES: 1. Add T suffix for tape and reel. Please refer to TB347 for details on reel specifications. 2. These Intersil Pbfree plastic packaged products employ special Pbfree material sets, molding compounds/die attach materials, and 100% matte tin plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pbfree soldering operations). Intersil Pbfree products are MSL classified at Pbfree peak reflow temperatures that meet or exceed the Pbfree requirements of IPC/JEDEC J STD For Moisture Sensitivity Level (MSL), please see device information page for ISL8014. For more information on MSL please see techbrief TB363. Pin Configuration ISL8014 (16 LD QFN) TOP VIEW NC LX LX NC VIN 1 12 PGND VIN 2 11 PGND VDD 3 10 SGND SYNCH 4 9 SGND Pin Descriptions EN NC PG VFB PIN NUMBER PIN NAME DESCRIPTION 1, 2 VIN Input supply voltage. Connect a 10µF ceramic capacitor to power ground. 3 VDD Input supply voltage for the analog circuitry. Connect to VIN pin. 5 EN Regulator enable pin. Keep the EN voltage low in disabled state until VIN settles or is above 2.5V. Enable the output when driven to high. Shut down the chip and discharge output capacitor when driven to low. Do not connect directly to VIN or leave this pin floating. 7 PG 1ms timer output. At powerup or EN HI, this output is a 1ms delayed PowerGood signal for the output voltage. 4 SYNCH Mode Selection pin. Connect to logic high or input voltage VDD for PWM mode. Connect to logic low or ground for PFM mode. Connect to an external function generator for synchronization with the negative edge trigger. Do not leave this pin floating. 14, 15 LX Switching node connection. Connect to one terminal of the inductor. 11, 12 PGND Power ground 9, 10 SGND Signal ground. 8 VFB Buck regulator output feedback. Connect to the output through a resistor divider for adjustable output voltage. For 0.8V output voltage, connect this pin to the output. 6, 13, 16 NC No connect. Exposed Pad The exposed pad must be connected to the SGND pin for proper electrical performance. Place as much vias as possible under the pad connecting to SGND plane for optimal thermal performance. 2 FN6576.4

3 Typical Application INPUT 2.7V TO 5.5V VIN LX L 1.5µH OUTPUT 1.8V C1 2 x 22µF R1 100k VDD ISL8014 PGND C2 2 x 22µF R2 124k C3 47pF PG VFB EN R3 100k SYNCH SGND FIGURE 1. TYPICAL APPLICATION DIAGRAM Block Diagram SYNCH EN SOFT Soft START SHUTDOWN BANDGAP 0.8V 3pF EAMP 27pF 390k OSCILLATOR COMP SHUTDOWN PWM/PFM LOGIC CONTROLLER PROTECTION DRIVER VIN LX PGND VFB 6k SLOPE Slope COMP CSA OCP 1.4V PG SGND 0.736V 1ms DELAY SKIP 0.5V ZEROCROSS SENSING 0.2V SCP FIGURE 2. FUNCTIONAL BLOCK DIAGRAM 3 FN6576.4

4 Absolute Maximum Ratings (Reference to GND) VIN, VDD V to 6V (DC) or 7V (20ms) EN, SYNCH, PG V to VIN 0.3V LX V (100ns)/0.3V (DC) to 6.5V (DC) or 7V (20ms) VFB V to 2.7V Recommended Operating Conditions VIN Supply Voltage Range V to 5.5V Load Current Range A to 4A Ambient Temperature Range C to 85 C Thermal Information Thermal Resistance (Typical, Notes 4, 5)θ JA ( C/W)θ JC ( C/W) 16 Ld 4x4 QFN Package Junction Temperature Range C to 125 C Storage Temperature Range C to 150 C PbFree Reflow Profile see link below CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and result in failures not covered by warranty. NOTE: 4. θ JA is measured in free air with the component mounted on a high effective thermal conductivity test board with direct attach features. See Tech Brief TB θ JC, case temperature location is at the center of the exposed metal pad on the package underside. See Tech Brief TB379. Electrical Specifications Unless otherwise noted, all parameter limits are established over the recommended operating conditions and the typical specification are measured at the following conditions: T A = 40 C to 85 C, V IN = 3.6V, EN = VDD, unless otherwise noted. Typical values are at T A = 25 C. Boldface limits apply over the operating temperature range, 40 C to 85 C. PARAMETER SYMBOL TEST CONDITIONS MIN (Note 7) TYP MAX (Note 7) UNITS INPUT SUPPLY V DD Undervoltage Lockout Threshold V UVLO Rising, no load V Falling, no load V Quiescent Supply Current I VIN SYNCH = GND, no load at the output 35 µa SYNCH = GND, no load at the output and no switches switching SYNCH = VDD, F S = 1MHz, no load at the output µa ma Shut Down Supply Current I SD V IN = 5.5V, EN = low µa OUTPUT REGULATION Reference Voltage V REF V VFB Bias Current I VFB VFB = 0.75V 0.1 µa Line Regulation V IN = V O 0.5V to 5.5V (minimal 2.7V) 0.2 %/V SoftStart Ramp Time Cycle 1 ms OVERCURRENT PROTECTION Current Limit Blanking Time t OCON 17 Clock pulses Overcurrent and Auto Restart Period t OCOFF 4 SS cycle Switch Current Limit I LIMIT (Note 6) A Peak Skip Limit I SKIP (Note 6) 1.3 A COMPENSATION Error Amplifier TransConductance 20 µa/v TransResistance RT Ω 4 FN6576.4

5 Electrical Specifications Unless otherwise noted, all parameter limits are established over the recommended operating conditions and the typical specification are measured at the following conditions: T A = 40 C to 85 C, V IN = 3.6V, EN = VDD, unless otherwise noted. Typical values are at T A = 25 C. Boldface limits apply over the operating temperature range, 40 C to 85 C. (Continued) PARAMETER SYMBOL TEST CONDITIONS MIN (Note 7) TYP MAX (Note 7) UNITS LX PChannel MOSFET ONResistance NChannel MOSFET ONResistance V IN = 5V, I O = 200mA mω V IN = 2.7V, I O = 200mA mω V IN = 5V, I O = 200mA mω V IN = 2.7V, I O = 200mA mω LX Maximum Duty Cycle 100 % PWM Switching Frequency f S MHz LX Minimum OnTime SYNCH = High 140 ns PG Output Low Voltage Sinking 1mA 0.3 V Delay Time (Rising Edge) ms PG Pin Leakage Current PG = V IN = 3.6V µa PGOOD Rising Threshold Percentage of regulation voltage % PGOOD Falling Threshold Percentage of regulation voltage % PGOOD Delay Time (Falling Edge) 15 µs EN, SYNCH Logic Input Low 0.4 V Logic Input High 1.4 V Synch Logic Input Leakage Current Enable Logic Input Leakage Current I SYNCH Pulled up to 5.5V µa I EN µa Thermal Shutdown 140 C Thermal Shutdown Hysteresis 25 C NOTES: 6. Limits established by characterization and are not production tested. 7. Parameters with MIN and/or MAX limits are 100% tested at 25 C, unless otherwise specified. Temperature limits established by characterization and are not production tested. 5 FN6576.4

6 Typical Operating Performance 100 (Unless otherwise noted, operating conditions are: T A = 25 C, V VIN = 2.5V to 5.5V, EN = V IN, SYNCH = 0V, L = 1.5µH, C 1 = 2x22µF, C 2 = 2x22µF, I OUT = 0A to 4A). 100 EFFICIENCY (%) V OUTPWM 1.8V OUTPWM 1.5V OUTPWM 1.2V OUTPWM EFFICIENCY (%) V OUTPFM 1.8V OUTPFM 1.5V OUTPFM 1.2V OUTPFM FIGURE 3. EFFICIENCY vs LOAD (1MHz 3.3 V IN PWM) FIGURE 4. EFFICIENCY vs LOAD (1MHz 3.3 V IN PFM) EFFICIENCY (%) V OUTPWM1.8VOUTPWM 1.5VOUTPWM 3.3V OUTPWM 1.2V OUTPWM EFFICIENCY (%) V OUTPFM 1.5V 2.5V OUTPFM 1.8V OUTPFM OUTPFM 3.3V OUTPFM FIGURE 5. EFFICIENCY vs LOAD (1MHz 5V IN PWM) FIGURE 6. EFFICIENCY vs LOAD (1MHz 5V IN PFM) POWER DISSIPATION (W) V INPWM 3.3V INPFM 5V INPFM 3.3V INPWM FIGURE 7. POWER DISSIPATION vs LOAD (1MHz, V OUT = 1.8V) POWER DISSIPATION (mw) V IN (V) FIGURE 8. POWER DISSIPATION WITH NO LOAD vs V IN (PWM V OUT = 1.8V) 6 FN6576.4

7 Typical Operating Performance 0.25 (Unless otherwise noted, operating conditions are: T A = 25 C, V VIN = 2.5V to 5.5V, EN = V IN, SYNCH = 0V, L = 1.5µH, C 1 = 2x22µF, C 2 = 2x22µF, I OUT = 0A to 4A). (Continued) 1.24 POWER DISSIPATION (mw) V IN (V) OUTPUT VOLTAGE (V) V INPFM 3.3V INPWM 5V INPWM 5V INPFM FIGURE 9. POWER DISSIPATION WITH NO LOAD vs V IN (PFM V OUT = 1.8V) FIGURE 10. V OUT REGULATION vs LOAD (1MHz, V OUT = 1.2V) OUTPUT VOLTAGE (V) V INPFM 5V INPWM 5V INPFM 3.3V INPWM FIGURE 11. V OUT REGULATION vs LOAD (1MHz, V OUT = 1.5V) OUTPUT VOLTAGE (V) V INPFM 5V INPFM 5V INPWM 3.3V INPWM FIGURE 12. V OUT REGULATION vs LOAD (1MHz, V OUT = 1.8V) OUTPUT VOLTAGE (V) V INPFM 5V INPFM 5V INPWM 3.3V INPWM OUTPUT VOLTAGE (V) V INPFM 5V INPWM 4.5V INPFM 4.5V INPWM FIGURE 13. V OUT REGULATION vs LOAD (1MHz, V OUT = 2.5V) FIGURE 14. V OUT REGULATION vs LOAD (1MHz, V OUT = 3.3V) 7 FN6576.4

8 Typical Operating Performance (Unless otherwise noted, operating conditions are: T A = 25 C, V VIN = 2.5V to 5.5V, EN = V IN, SYNCH = 0V, L = 1.5µH, C 1 = 2x22µF, C 2 = 2x22µF, I OUT = 0A to 4A). (Continued) OUTPUT VOLTAGE (V) A LOAD PWM 0A LOAD PWM OUTPUT VOLTAGE (V) A LOAD 0A LOAD INPUT VOLTAGE (V) FIGURE 15. OUTPUT VOLTAGE REGULATION vs VIN (PWM V OUT = 1.8 ) INPUT VOLTAGE (V) FIGURE 16. OUTPUT VOLTAGE REGULATION vs VIN (PFM V OUT = 1.8V) V OUT RIPPLE 20mV/DIV V OUT RIPPLE 20mV/DIV IL 0.5A/DIV IL 0.5A/DIV FIGURE 17. STEADY STATE OPERATION AT NO LOAD (PWM) FIGURE 18. STEADY STATE OPERATION AT NO LOAD (PFM) V OUT RIPPLE 50mV/DIV IL 2A/DIV V OUT RIPPLE 20mV/DIV FIGURE 19. STEADY STATE OPERATION WITH FULL LOAD FIGURE 20. MODE TRANSITION CCM TO DCM 8 FN6576.4

9 Typical Operating Performance (Unless otherwise noted, operating conditions are: T A = 25 C, V VIN = 2.5V to 5.5V, EN = V IN, SYNCH = 0V, L = 1.5µH, C 1 = 2x22µF, C 2 = 2x22µF, I OUT = 0A to 4A). (Continued) V OUT RIPPLE 50mV/DIV V OUT RIPPLE 50mV/DIV FIGURE 21. MODE TRANSITION DCM TO CCM FIGURE 22. LOAD TRANSIENT (PWM) EN 5V/DIV V OUT RIPPLE 50mV/DIV V OUT 0.5V/DIV PG 5V/DIV FIGURE 23. LOAD TRANSIENT (PFM) FIGURE 24. SOFTSTART WITH NO LOAD (PWM) EN 5V/DIV EN 5V/DIV V OUT 0.5V/DIV V OUT 0.5V/DIV PG 5V/DIV PG 5V/DIV FIGURE 25. SOFTSTART AT NO LOAD (PFM) FIGURE 26. SOFTSTART WITH PREBIASED 1V 9 FN6576.4

10 Typical Operating Performance (Unless otherwise noted, operating conditions are: T A = 25 C, V VIN = 2.5V to 5.5V, EN = V IN, SYNCH = 0V, L = 1.5µH, C 1 = 2x22µF, C 2 = 2x22µF, I OUT = 0A to 4A). (Continued) EN 2V/DIV EN 5V/DIV V OUT 0.5V/DIV IL 2A/DIV PG 5V/DIV V OUT 0.5V/DIV PG 5V/DIV FIGURE 27. SOFTSTART AT FULL LOAD FIGURE 28. SOFTDISCHARGE SHUTDOWN SYNCH 2V/DIV SYNCH 2V/DIV V OUT RIPPLE 20mV/DIV V OUT RIPPLE 20mV/DIV FIGURE 29. STEADY STATE OPERATION AT NO LOAD WITH FREQUENCY = 2MHz FIGURE 30. STEADY STATE OPERATION AT FULL LOAD WITH FREQUENCY = 2MHz SYNCH 2V/DIV SYNCH 2V/DIV V OUT RIPPLE 20mV/DIV IL 0.5A/DIV V OUT RIPPLE 20mV/DIV FIGURE 31. STEADY STATE OPERATION AT NO LOAD WITH FREQUENCY = 4MHz FIGURE 32. STEADY STATE OPERATION AT FULL LOAD (PWM) WITH FREQUENCY = 4MHz 10 FN6576.4

11 Typical Operating Performance (Unless otherwise noted, operating conditions are: T A = 25 C, V VIN = 2.5V to 5.5V, EN = V IN, SYNCH = 0V, L = 1.5µH, C 1 = 2x22µF, C 2 = 2x22µF, I OUT = 0A to 4A). (Continued) IL 2A/DIV V OUT 0.5V/DIV V OUT 1V/DIV PG 5V/DIV PG 5V/DIV IL 2A/DIV FIGURE 33. OUTPUT SHORT CIRCUIT FIGURE 34. OUTPUT SHORT CIRCUIT RECOVERY OUTPUT CURRENT (A) OCP_3.3V IN OCP_5V IN TEMPERATURE ( C) FIGURE 35. OUTPUT CURRENT LIMIT vs TEMPERATURE Theory of Operation The ISL8014 is a stepdown switching regulator optimized for batterypowered handheld applications. The regulator operates at 1MHz fixed switching frequency under heavy load conditions to allow smaller external inductors and capacitors to be used for minimal printedcircuit board (PCB) area. At light load, the regulator reduces the switching frequency, unless forced to the fixed frequency, to minimize the switching loss and to maximize the battery life. The quiescent current when the output is not loaded is typically only 35µA. The supply current is typically only 0.1µA when the regulator is shut down. PWM Control Scheme Pulling the SYNCH pin HI (>2.5V) forces the converter into PWM mode, regardless of output current. The ISL8014 employs the currentmode pulsewidth modulation (PWM) control scheme for fast transient response and pulsebypulse current limiting. Figure 2 shows the block diagram. The current loop consists of the oscillator, the PWM comparator, current sensing circuit and the slope compensation for the current loop stability. The gain for the current sensing circuit is typically 200mV/A. The control reference for the current loops comes from the error amplifier's (EAMP) output. The PWM operation is initialized by the clock from the oscillator. The PChannel MOSFET is turned on at the beginning of a PWM cycle and the current in the MOSFET starts to ramp up. When the sum of the current amplifier CSA and the slope compensation (237mV/µs) reaches the control reference of the current loop, the PWM comparator COMP sends a signal to the PWM logic to turn off the PMOSFET and turn on the NChannel MOSFET. The NMOSFET stays on until the end of the PWM cycle. Figure 36 shows the typical operating waveforms during the PWM operation. The dotted lines illustrate the sum of the slope compensation ramp and the currentsense amplifier s CSA output. The output voltage is regulated by controlling the V EAMP voltage to the current loop. The bandgap circuit outputs a 0.8V reference voltage to the voltage loop. The feedback signal comes from the VFB pin. The softstart block only affects the operation during the startup and 11 FN6576.4

12 will be discussed separately. The error amplifier is a transconductance amplifier that converts the voltage error signal to a current output. The voltage loop is internally compensated with the 27pF and 390kΩ RC network. The maximum EAMP voltage output is precisely clamped to 1.6V. V EAMP V CSA DUTY CYCLE I L V OUT FIGURE 36. PWM OPERATION WAVEFORMS SKIP Mode Pulling the SYNCH pin LO (<0.4V) forces the converter into PFM mode. The ISL8014 enters a pulseskipping mode at light load to minimize the switching loss by reducing the switching frequency. Figure 37 illustrates the skipmode operation. A zerocross sensing circuit shown in Figure 2 monitors the NMOSFET current for zero crossing. When 8 consecutive cycles of the inductor current crossing zero are detected, the regulator enters the skip mode. During the eight detecting cycles, the current in the inductor is allowed to become negative. The counter is reset to zero when the current in any cycle does not cross zero. Once the skip mode is entered, the pulse modulation starts being controlled by the SKIP comparator shown in Figure 2. Each pulse cycle is still synchronized by the PWM clock. The PMOSFET is turned on at the clock's rising edge and turned off when the output is higher than 1.5% of the nominal regulation or when its current reaches the peak Skip current limit value. Then the inductor current is discharging to 0A and stays at zero. The internal clock is disabled.the output voltage reduces gradually due to the load current discharging the output PWM capacitor. When the output voltage drops to the nominal voltage, the PMOSFET will be turned on again at the rising edge of the internal clock as it repeats the previous operations. The regulator resumes normal PWM mode operation when the output voltage drops 1.5% below the nominal voltage. Synchronization Control The frequency of operation can be synchronized up to 4MHz by an external signal applied to the SYNCH pin. The falling edge on the SYNCH triggers the rising edge of the LX pulse. Make sure that the minimum on time of the LX node is greater than 140ns. Overcurrent Protection The overcurrent protection is realized by monitoring the CSA output with the OCP comparator, as shown in Figure 2. The current sensing circuit has a gain of 200mV/A, from the PMOSFET current to the CSA output. When the CSA output reaches 1.4V, which is equivalent to 5.7A for the switch current, the OCP comparator is tripped to turn off the PMOSFET immediately. The overcurrent function protects the switching converter from a shorted output by monitoring the current flowing through the upper MOSFET. Upon detection of overcurrent condition, the upper MOSFET will be immediately turned off and will not be turned on again until the next switching cycle. Upon detection of the initial overcurrent condition, the overcurrent fault counter is set to 1. If, on the subsequent cycle, another overcurrent condition is detected, the OC fault counter will be incremented. If there are 17 sequential OC fault detections, the regulator will be shut down under an overcurrent fault condition. An overcurrent fault condition will result in the regulator attempting to restart in a hiccup mode within the delay of four softstart periods. At the end of the fourth softstart wait period, the fault counters are reset and softstart is attempted again. If the overcurrent condition goes away during the delay of four softstart periods, the output will resume back into regulation point after hiccup mode expires. PFM CLOCK 8 CYCLES PFM CURRENT LIMIT I L 0 LOAD CURRENTT NOMINAL 1.5% V OUT NOMINAL FIGURE 37. SKIP MODE OPERATION WAVEFORMS 12 FN6576.4

13 ShortCircuit Protection The shortcircuit protection SCP comparator monitors the VFB pin voltage for output shortcircuit protection. When the VFB is lower than 0.2V, the SCP comparator forces the PWM oscillator frequency to drop to 1/3 of the normal operation value. This comparator is effective during startup or an output shortcircuit event. PG During powerup, the opendrain power good output holds low for about 1ms after V OUT reaches the regulation voltage. The PG output also serves as a 1ms delayed the Power Good signal when the pullup resistor R 1 is installed. Soft StartUp The softstartup reduces the inrush current during the startup. The softstart block outputs a ramp reference to the input of the error amplifier. This voltage ramp limits the inductor current as well as the output voltage speed so that the output voltage rises in a controlled fashion. When VFB is less than 0.2V at the beginning of the softstart, the switching frequency is reduced to 1/3 of the nominal value so that the output can start up smoothly at light load condition. During softstart, the IC operates in the SKIP mode to support prebiased output condition. UVLO When the input voltage is below the undervoltage lockout (UVLO) threshold, the regulator is disabled. To adjust the voltage level of power on and UVLO, use a resistive divider across EN. The input voltage programming resistor R 4 will depend on on the bottom resistor R 5, as referred to in Figure 38. The value of R 5 is typically between 10kΩ and 100kΩ. Enable EN 1V V IN The enable (EN) input allows the user to control the turning on or off the regulator for purposes such as powerup sequencing. When the regulator is enabled, there is typically a 600µs delay for waking up the bandgap reference and then the softstartup begins. It is recommended that the EN voltage should be kept logic low (less than 400mV), until V IN reaches 2.5V. Refer to Figures 38 and 39 for suggested circuit implementation with V IN slew rate. R4 R5 FIGURE 38. EXTERNAL RESISTOR DIVIDER C V (VOLTS) 2.5V FIGURE 39. CIRCUIT IMPLEMENTATION WITH V IN SLEW RATE Let T equal the rise time of V IN. Select the ratio of R 5 and R 4 such that the voltage is 1.4V (minimum enable logic high threshold) when V IN is equal to or greater than 2.5V. Set R 5 between 10kΩ to 100kΩ, and use Equation 1 to determine R 4 : Where V IN is greater than or equal to 2.5V. Then select C such that the equivalent time constant is at least 2x the rise time, T. This will delay the EN voltage enough so that the overall EN voltage is less than 400mV by the time V IN reaches 2.5V. Use Equation 2 to get C: Where T is the rise time of V IN As an example, let V IN = 5V with rise time, T = 10ms. Then R 4 = 56.2kΩ, R 5 = 71.5kΩ, and C = 0.68µF are used to insure that V IN was >2.5V and the EN voltage was <400mV. Discharge Mode (SoftStop) When a transition to shutdown mode occurs or the VIN UVLO is set, the outputs discharge to GND through an internal 100Ω switch. Power MOSFETs The power MOSFETs are optimized for best efficiency. The ONresistance for the PMOSFET is typically 50mΩ and the ONresistance for the NMOSFET is typically 50mΩ. 100% Duty Cycle T VIN EN <400mV t (TIME) R R 5 ( V IN 1.4V) 4 = (EQ. 1) 1.4V 2 T C (EQ. 2) R 4 R 5 The ISL8014 features 100% duty cycle operation to maximize the battery life. When the battery voltage drops to a level that the ISL8014 can no longer maintain the regulation at the output, the regulator completely turns on the PMOSFET. The maximum dropout voltage under the 100% dutycycle operation is the product of the load current and the ONresistance of the PMOSFET. 13 FN6576.4

14 Thermal ShutDown The ISL8014 has builtin thermal protection. When the internal temperature reaches 140 C, the regulator is completely shut down. As the temperature drops to 115 C, the ISL8014 resumes operation by stepping through the softstart. Applications Information Output Inductor and Capacitor Selection To consider steady state and transient operations, ISL8014 typically uses a 1.5µH output inductor. The higher or lower inductor value can be used to optimize the total converter system performance. For example, for higher output voltage 3.3V application, in order to decrease the inductor current ripple and output voltage ripple, the output inductor value can be increased. It is recommended to set the ripple inductor current approximately 30% of the maximum output current for optimized performance. The inductor ripple current can be expressed as shown in Equation 3: V O V O 1 V (EQ. 3) IN ΔI = L f S The inductor s saturation current rating needs to be at least larger than the peak current. The ISL8014 protects the typical peak current 6A. The saturation current needs be over 7A for maximum output current application. ISL8014 uses internal compensation network and the output capacitor value is dependent on the output voltage. The ceramic capacitor is recommended to be X5R or X7R. The recommended X5R or X7R minimum output capacitor values are shown in Table 1. In Table 1, the minimum output capacitor value is given for the different output voltage to make sure that the whole converter system is stable. Additional output capacitance should be added for better performances in applications where high load transient or low output ripple is required. It is recommended to check the system level performance along with the simulation model. Output Voltage Selection The output voltage of the regulator can be programmed via an external resistor divider that is used to scale the output voltage relative to the internal reference voltage and feed it back to the inverting input of the error amplifier. Refer to Figure 1. The output voltage programming resistor, R 3, will depend on the value chosen for the feedback resistor and the desired output voltage of the regulator. The value for the feedback resistor is typically between 10kΩ and 100kΩ, as shown in Equation 4. R R 2 0.8V 3 = (EQ. 4) V OUT 0.8V If the output voltage desired is 0.8V, then R 3 is left unpopulated and R 2 is shorted. There is a leakage current from VIN to LX. It is recommended to preload the output with 10µA minimum. For better performance, add 47pF in parallel with R 2 (100kΩ). Input Capacitor Selection The main functions for the input capacitor are to provide decoupling of the parasitic inductance and to provide filtering function to prevent the switching current flowing back to the battery rail. Two 22µF X5R or X7R ceramic capacitors are a good starting point for the input capacitor selection. TABLE 1. OUTPUT CAPACITOR VALUE vs V OUT V OUT (V) C OUT (µf) L (µh) x ~ x ~ x ~ x ~ x ~ x ~ x ~4.7 For additional products, see Intersil products are manufactured, assembled and tested utilizing ISO9000 quality systems as noted in the quality certifications found at Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see 14 FN6576.4

15 Revision History The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to web to make sure you have the latest Rev. DATE REVISION CHANGE 11/23/09 FN Updated on page 13 in UVLO section, last sentence from...programming resistor R5..., The value of R4... to...programming resistor R4..., The value of R5.... Replaced Figure 38, Removed Equation after Figure 38. Reworded last sentence in Enable section from It is necessary to keep the voltage on the EN low until Vin is greater than 2.5V to It is recommended that the EN voltage should be kept logic low (less than 400mV), until VIN reaches 2.5V. Refer to Figure 39 for suggested circuit implementation with VIN slew rate. Added Figure 39. Added Equations 1 and 2 and referencing text. Added Revision History and Products information. Moved SoftStart section to read after PG section on page 13, changed "R4" to "R5" in last sentence of UVLO section, added reference of both Figures 38 and 39 in Enable section. 09/10/09 FN /10/09: Page 6; Revised last sentence of EN section from: "Do not leave this pin floating." TO:"Do not connect directly to VIN or leave this pin floating." 9/2/09: Page 2: Order Info: Added MSL link to Order Info per new standard Page 2: Revised Typical Application Diagram Pages 45: Per new Intersil standard: Added "Boldface limits apply over the operating temperature range, 40 C to 85 C." to common conditions of Electrical Specs table. Bolded MIN MAX columns where applicable. Moved "Parameters with MIN and/or MAX limits are 100% tested at 25 C, unless otherwise specified. Temperature limits established by characterization and are not production tested." from common conditions of Electrical Specs table to note in Min Max columns. Page 6: Added following sentence to EN pin description: " Keep the EN voltage low in disabled state until Vin settle or above 2.5V." Revised "FIGURE 37. SKIP MODE OPERATION WAVEFORMS Page 14: Added FIGURE 38. EXTERNAL RESISTOR DIVIDER graphic and following sentence to UVLO section: "To adjust the voltage level of power on and UVLO, use a resistive divider across EN. The input voltage programming resistor R5 will depend on on the bottom resistor R4, as referred to in Figure 38. The value of R4 is typically between 10kohm and 100kohm." Added equation 1 to UVLO section: Added following sentence to Enable section: "It is necessary to keep the voltage of the EN low until Vin is greater than 2.5V." 08/04/08 FN Added to VIN, VDD and LX in Abs Max Rating (DC) or 7V (20ms). Added Intersil Standards as follows: Added to Electrical Specs conditions at top overtemp note. Updated POD L16.4x4 to latest version. 12/20/07 FN Removed the MIN and MAX value of "Peak Skip Limit " in the EC table at page 4. Replaced the TransResistance (RT) value "0.18" into "0.17" for MIN and "0.22" into "0.23" for MAX in the EC table on page 4. 11/28/07 FN Initial Release to web ISL8014 Products Intersil Corporation is a leader in the design and manufacture of highperformance analog semiconductors. The Company's products address some of the industry's fastest growing markets, such as, flat panel displays, cell phones, handheld products, and notebooks. Intersil's product families address power management and analog signal processing functions. Go to for a complete list of Intersil product families. *For a complete listing of Applications, Related Documentation and Related Parts, please see the respective device information page on intersil.com: ISL8014 To report errors or suggestions for this datasheet, please go to FITs are available from our website at 15 FN6576.4

16 Package Outline Drawing L16.4x4 16 LEAD QUAD FLAT NOLEAD PLASTIC PACKAGE Rev 6, 02/08 4X A B 13 12X PIN #1 INDEX AREA 6 PIN 1 INDEX AREA ± (4X) 0.15 TOP VIEW 16X BOTTOM VIEW M C A B / 0.05 SEE DETAIL "X" ( 3. 6 TYP ) 1.00 MAX ( ) ( 12X ) SIDE VIEW 0.10 C C BASE PLANE SEATING PLANE 0.08 C TYPICAL RECOMMENDED LAND PATTERN ( 16X ) ( 16 X 0. 8 ) C 0. 2 REF MIN MAX. DETAIL "X" NOTES: Dimensions are in millimeters. Dimensions in ( ) for Reference Only. Dimensioning and tolerancing conform to AMSE Y14.5m1994. Unless otherwise specified, tolerance : Decimal ± 0.05 Dimension b applies to the metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. Tiebar shown (if present) is a nonfunctional feature. The configuration of the pin #1 identifier is optional, but must be located within the zone indicated. The pin #1 identifier may be either a mold or mark feature. 16 FN6576.4